In this study I will investigate the role of melanin and the membrane interactions between the retinal neural and pigment epithelia on the growth of central retinal axons during mammalian embryonic eye development. Ferret embryos will be exposed to chloroquine, a drug which has a high affinity for melanin in the developing pigment epithelium, during the period when melanogenesis and retinal axon differentiation are occurring in the developing eye. These animals will be examined post partum, by the autoradiographic tracing method, to determine if this drug has had any effect on the central growth of retinogeniculate axons. In this way we can establish a more precise role for melanin in specifying central retinal axon growth. An ultrastructural analysis of the distribution and morphology of gap junctions between cells of the developing retinal pigment and neural epithelia will be done at different stages of eye development to establish what role membrane specializations have in specifying the central growth of retinal axons. Related studies indicate that gap junctions may be critical in determining the control of growth and differentiation in developing systems. Comparisons between albino and pigmented embryonic eyes at the same stages of development, will be made to quantify the differences which pilot studies indicate are present. The distribution of tight junctions and micropinocytotic activity will also be examined to determine if there are detectable changes in their distribution during eye development.